Modern motor vehicles are increasingly being equipped with functions such as Adaptive Cruise Control (hereinafter referred to as ACC) which make it possible for the speed of the vehicle to be regulated to a target speed predefined by the vehicle driver and/or adapted to the speed of the vehicle traveling ahead. Corresponding regulation systems are known for example from EP 1245428 A2, which is incorporated by reference. Said functions or regulation systems are realized by virtue of vehicles being equipped with at least one long-range sensor, such as a radar or lidar sensor, in order to measure the separation distance to a vehicle traveling ahead or to a nearby obstruction and automatically regulate said separation distance to a predefined, preferably speed-dependent target separation distance. Owing to the configuration of the regulation systems, the automatic separation-distance regulation can usually be activated only above a certain minimum vehicle speed.
Extended functionality is afforded by ACC systems with a stop-and-go function which, when required, automatically brake the vehicle to a standstill, or stop the vehicle, within a predefined time, for example in order to prevent a collision with the vehicle traveling ahead when arriving at the tail end of a traffic jam. Automatic restarting is also possible when there is an adequate separation distance to the vehicle traveling ahead and, expediently, further preconditions are met such as the exceedance of a minimum standstill time or the confirmation of a starting request by the vehicle driver. A confirmation by actuation of the accelerator pedal is disclosed for example in EP 1442917 A2, which is incorporated by reference. In the case of the stop-and-go function, the one or more long-range sensors are combined with one or more short-range sensors, preferably with multiple ultrasound sensors, in order to measure the remote and close regions in front of the vehicle.
For example, EP 2152538 B1, which is incorporated by reference, discloses a device and a method for controlling the following separation distance. The vehicle speed and a following separation distance between a vehicle traveling ahead and the subject vehicle are measured. A demanded acceleration is thereupon calculated and transmitted to a control device which controls the following separation distance to the vehicle traveling ahead on the basis of the demanded acceleration. If the vehicle traveling ahead stops, a stopping controller is activated. Here, a standstill state of the subject vehicle is identified on the basis of the demanded acceleration and a real vehicle speed which, using conventional sensors, can no longer be distinguished from zero; this ensures a smooth stopping process.
In the case of the known ACC systems with stop-and-go function, the automatic braking of the vehicle to a standstill takes place within a defined time period, wherein, for safety reasons, the stopping process is completed with a predetermined safe separation distance of typically 5 m to the vehicle in front. This has the advantage that the restart requires only relatively low dynamics. Said systems are suitable in particular for journeys on a highway or freeway, because on these roads, maintaining a large separation distance to the vehicle traveling ahead is mandatory. By contrast, in the case of inner-city journeys or for example in traffic jam situations on highways, the maintained safe separation distance to the vehicle in front constitutes a potential hazard because other vehicles from the adjacent lanes may cut into the gap.
EP 2176109 B1, which is incorporated by reference, discloses a separation-distance regulation system with automatic stopping and/or starting function for motor vehicles, having a separation-distance-measuring long-range sensor, a separation-distance-measuring ultrasound sensor, and a control unit which is designed to intervene in the longitudinal control of the subject vehicle as a function of the separation distance, measured by the long-range sensor, to a vehicle traveling ahead. If the measured separation distance is less than the range of the ultrasound sensor, the functionality of the ultrasound sensor is verified, whereupon separation-distance regulation is performed, within the context of the stopping and/or starting function, on the basis of the signal of the ultrasound sensor.